The fibrotic lung disorders represent 15% of the non-infectious, non-malignant lung diseases; they are often progressive and can be fatal. The fibrosis results from damage caused by inflammatory cells and subsequent proliferation of mesenchymal cells, driven by mediators released by alveolar macrophages. The primary mediators are platelet-derived growth factor, fibronectin and insulin-like growth factor-I. Other mediators released by stimulated alveolar macrophages include tumor necrosis factor, transforming growth factor-beta and interleukin 1. With knowledge of the specific processes involved, strategies can be developed to modulate these mediators as therapy for these disorders.